Continue the study on the nature of action of dusts that lead to death of insects by desiccation. This involves distinguishing between and evaluating quantitatively the physiological vs. physico-chemical effects. Also localizing the site of both effects with the help of drug and electron microscopic studies. An examination of the nature of the lethal effect of desiccation by comparing midge species that can versus cannot be reversibly dehydrated. An electron microscope study of the degree of similarity or dissimilarity of the proventriculus and peritrophic membrane of larvae of mosquitoes and some of their relatives. Further experimental analysis of the desirable relationship between blood osmolarity of mosquitoes and the osmolarity of fixing fluids used for electron microscopy.